Apparatus fob thinning varnishes



g- 1939. R. AYRES ET AL 2,158,273

APPARATUS FOR THINNING VARNISHES Filed Feb. 3, 1957 I Hmv/d /?.@res 5625 L. Window 1NVENTOR M YAMD Patented Aug. 1, 1939 UNITED STATES APPARATUS FOR THINNING VARNISHES Harold R. Ayres, Chicago, Ill., and Seth L. Winslow, Parlin, N. J., assignors to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware Application February 3, 1937, Serial No. 123,814

1 Claim.

This invention relates to a method of preparing varnishes and more particularly to a method of thinning the hot resins.

In the preparation of varnishes it is customary to cook the resins and oils together, in an open kettle over a fire. When the mixturehas been cooked suificiently, the fire is dumped or' the kettle is taken from the fire and allowed to cool. When the mixture has cooled the thinners are poured in. Sometimes this is done by workmen who merely pour a can full of the thinner into the resin-oil mixture and sometimes it is done by means of a pipe line from the tank of thinner. In either case, there is a delay of several hours depending on the weather from the time the resin mixture is taken from the fire to the time the thinner is added.

As far as the applicants are aware, it has never been proposed to add the thinner to the hot resin-oil mixture in a closed tank for the reason that the temperature of the latter is very high; that is, of the order of 450 F. to 500 F. If the thinner should be added directly to this hot frothing mixture, it is very likely that it would burst into flame or at least be boiled ofi completely in a very short time. Another danger which would result in this procedure is that there may be static electricity present, the discharge of which would ignite the vapors arising from the kettle.

An object of the present invention is the provision of a method of thinning hot molten resins. Another object is the provision of an apparatus by which hot resin-oil mixtures may be thinned. Other objects will be apparent as the description of the invention proceeds.

These and other objects are accomplished by means of a novel apparatus which will be described in detail, and by a method in which the step of adding the thinner to the hot resin quickly and below the surface plays an important part.

In the drawing Figure 1 is a diagrammatic plan view of an apparatus suitable for carrying out the invention. Figure 2 is a diagrammatic side view of the ventilating system.

In the drawing, I represents the varnish kettle in which the resins, gums, oils, and ingredients of the varnish other than the thinner are cooked. In both figures, 24 is a hood and 2 represents the vent from which the vapors arising from the cooked varnish are drawn off. In Figure 1, 3 is the mixing tank and 4 is the tank in which the thinners are mixed before they are added to tank 3. A pump 5 driven by motor 6 is connected by pipe "I to the varnish kettle I. This pipe has universal joints which are not shown which enable the operator to-raise it and lower it from the tank 2. Also, connected to the pump is a pipe 8 which leads to the bottom of tank 3 and also a'pipe 9 which leads to tank 3 and by means of which the resin mixture may be pumped fromtank 'I' to tank3. These pipes are, of

course, provided with valves which are not shown but by'means of which any pipe line may be closed. Another pipe line 'IIJ leads from the bottom of tank 4 to the bottom of tank 3 and is also provided with suitable valves. Tank 3 is also provided with an agitator I I driven by motor I2. Tanks I3, I4, I5, and I6 are storages for the various thinners. These are connected by pipe line Il provided with suitablevalves to tank 4, and if necessary pumped by inserting a pump as indicated.

In Figure 2, the vapors arising from the kettle are drawn ofithrough the vent 2 where they come in contact with water spray I8. They are then further led downward in contact with the water spray I9 and upward in contact with spray 20 and are ledthrough vent 2I. 25

In the operation of the apparatus, the resin and oil components of the varnish are cooked until the proper viscosity is reached'in kettle I over a fire not shown. The kettle I is then drawn from the "fire and placed in the position shown in'Figure 1. The pipe I is then lowered into the kettle and the pump 5 started whereby the resin mixture is transferred through the pipe line 9 to the mixing tank 3. In, the meantime, the desired thinners in the correct proportions 3 are run or pumped from tanks I3, I4, I5, and I6 respectively into tank 4 where they are blended. The thinner mixture is then dropped through pipe I0 into tank 3 and the agitator II is started. When all of the thinner has been added, a :40 valve in pipe 9 is closed and a valve in line '8 and 23 is opened and the pump started which transfers the finished varnish to storage tanks not shown.

A vent 22 from tank 3 is shown and extends through water spray I8 and 20. Recovered thinners drop into tank as indicated where water spray I8 and 20 cools and collects the solid fumes and also cools the coil and condenses thinners from the vent.

When the hot resin-oil mixture is taken from the fire and placed under the hood 24, the vapors are drawn off through vent 2 and downward in contact with spray I8. The vapors then turn upward and again in contact with another water spray 20. These sprays remove all the tarry matter which would otherwise collect in the ventilating system. The vapors are then led off through pipe 2|. There is usually no solvent to recover when the apparatus is operated as just indicated. However, if the thinner is mixed in tank I instead of tank 3, there will be considerable solvent which will make it worth while to recover the same. In this alternate procedure,

the thinner is dropped from tank 4 through pipes V I0, 8, and 1 into tank I.

It has also been found convenient to mount some of the tanks on scales so that the batch may be weighed as filled. A scale fitted with a photoelectric cell may be used whereby the valves are opened by hand and closed automatically when the set weight has been run in.

While only one installation is shown, it will be understood that the units may be arranged in the form of a battery of two, four, six, or practically any number desired. The same ventilating system may be used for all units as well as the same solvent and finished varnish storage tanks. r 1 7 In one embodiment of the invention, the varnish ingredients aside from the thinners are placed in an open kettle provided with wheels. The kettle is usually filled and then rolled over a fire. The ingredients in the kettle which are primarily gums and oils are heated gradually until the correct formula temperature is reached. The heating is continued until the desired results are obtained as indicated by the volume, specific gravity, viscosity, or whatever indication is used 7 for the particular varnish. The kettle is then withdrawn and moved into the hood as indi-- cated in the drawing. The ingredients are still at a high temperature and large volumes of vapors arise and are drawn ofi through the ventilating system.

The thinners which have previously been weighed out and run through a tank are now ready for adding to the resin-oil mixture. It is essential in many typesv of varnish to add the thinner steadily to the cooked ingredients but not so quickly that the mixture will separate into layers. In other' varnishes it is advantageous to run the resin mixture into the oil, and in still further cases it has been found advantageous to mix the cooked material with the thinner simultaneously. Assuming that in the present example it is desired to add the thinner to the resin-oil mixture, the various ingredients of the thinner in the desired proportions are turned into a tank and mixed well. The thinner is then either dropped by gravity or pumped into the hot resin-oil mixture by means of a pipe which leads to the bottom of the mixing chamber. This chamber is fitted with an agitator as shown in the drawing and the varnish is well stirred while the thinner is being added.

If desired the thinner may be run into the ope kettle, but it has been found advantageous to pump the hot resin mixture into a closed mixing tank before the thinner is added. If it is desired to add the resin to the thinner this may apparently be done by running the thinner into the mixing tank and later adding the resin with agi-' tation as before; or, as another alternative, they may both be run into the mixing tank simultaneously.

In the preparation of varnishes details which appear to be very minor in character have a considerable influence on the properties of the finished varnish. For example, it is advantageous that the thinner be madeup before hand and run into the resin-oil mixture steadily. As suggested above, it is also important with. certain varnishes to run the resin into the thinner. Another detail which influences the finished varnishes is the rate of fiow of the thinner into the resin or vice versa.

On account of thinning at high temperatures in this'closed apparatus, it is possible to secure better control of the finished varnishes as they can be reduced at once without the long wait for a drop in temperature as is necessary when openkettle thinning is used. r A

The present invention also offers the advantage that the thinner and resin' mixture may be mixed while the latter is still very hot, thereby saving a number of hours during which time the varnish normally is allowed to cool.

It is apparent that many widely difierent embodiments of this invention may be made without departing from the spirit and scope thereof; and, therefore, it is not intended to be limited except as indicated in the appended claim.

We claim: I

Apparatus for thinning varnishes which comprises a series of tanks for containing solvents to be used in thinning the varnish, a mixing tank, a pipe line connecting the said tanks to the mixing tank, a second mixing tank and a pipe line leading directly from the first mixing tank to a point near the bottom of the second mixing tank,

means for agitating the contents of the second mixing tank, a pump, a pipeline leading froma point near the bottom of the second mixing tank to the pump, a cooking kettle at the lowest point in the system, a pipe line leading directly from the cooking kettle to the pump and a further pipe line connected thereto leading to the bottom of the said second mixing tank whereby hot varnish may be pumped from the cooking kettle upwardly through the pump to the pipe line leading to the point near the bottom of the said second mixing tank and whereby thinner may be run from the bottom of the said second mixing tank downwardly by gravity to the cooking kettle.

HAROLD R. AYRES.

SETH L. WINSLOW. 

